1. Field of the Invention
The present invention relates to a sound motion picture camera and its sound motion picture system.
2. Description of the Prior Art
Many motion picture films are available with sound information recorded with the picture information. Two methods exist for this sound information on the film methods, optical and magnetic. While the former method makes it impossible simply to erase already recorded sound and to record new sound on the film, the latter method allows for erasing of the already recorded sound and recording of new sound "on the erased portion or overlapping" the already recorded sound.
In the field of 8 m/m size films, however, until a few years ago, there was no film capable of magnetic recording of sound information in the market, and therefore the optical recording method prevailed. Consequently, all the sound motion picture projectors of the type using 8 m/m size films which were available a few years ago employed the method by which the sound information optically recorded on the film is reproduced optically. Recently, however, 8 m/m size films capable of magnetically recording sound information came on the market, sold under the trade name "Sound Movie Film" from Eastman Kodak Company in U.S.A. In response to this, a rapidly increasing number of sound motion picture cameras capable of magnetically recording sound information on the film in combination with sound motion picture projectors capable of magnetically reproducing the sound information of the film are being developed.
The above mentioned "Sound Movie Film" as disclosed in U.S. Pat. No. 3,858,968 has a main stripe of magnetic recording material along one edge of one surface of the film and a balance stripe of magnetic recording material along the other edge of the same surface of the film, the balance stripe being located adjacent a series of perforations in the film and the light sensitive emulsion on the film typically being located on the opposite (lower) surface of the film. This film is made with a balance stripe in combination with the main stripe because when only the main stripe is applied to the base material of the film, the film tends to produce an inclined coil as it is wound up. The balance stripe compensates for the difference in thickness between the two sides of the film.
With this type film, therefore, sound information is usually recorded only on the main stripe, while the balance stripe is not used for recording sound. This fact is by no means due to the impossibility of recording sound information on the balance stripe, but to the quality of extreme inferiority of the sound reproduced from the balance stripe in quality to that of the main stripe because the width of the balance stripe is considerably narrower than that of the main stripe. If we are not concerned about this loss of sound quality, it is of course possible to make use of the balance stripe for recording sound information, as, for example, disclosed in DOLS 2,417,095. In this motion picture system, the film is prepared with background music recorded on the main stripe. Then this film is used by a camera to record picture information together with corresponding sound information, the latter being recorded on the balance stripe. The sound information recorded on the balance stripe by the camera is transferred to the main stripe of the same film by an editor having recording/reproducing heads respectively corresponding to the main and balance stripe. Thus the sound information of the balance stripe, such as dialog or narration is overlapped on that of the main stripe such as background music. Alternatively, after the aforementioned sound information of the main stripe has been erased at portions, the sound information recorded on the balance stripe by the camera is transferred to the main stripe at the erased portions.
In the field of tape recording, it is very common practice to edit the original sound on a tape having a strip of magnetic recording material. There are two editing methods: "sound on sound" and "sound with sound". The sound-on-sound editing method comprises recording a sound signal on a first track of a magnetic tape, reproducing it by a recording/reproducing head provided for said the track, mixing the reproduced sound, while being heard, with a new sound signal, and supplying the mixed sound signals with overlapping of a bias to a second recording/reproducing head provided for a second track of the tape. The original sound signal and the new sound signal are, thus recorded on said second track on the tape in unison. When reproduced by operating the second recording/reproducing head, both of the sound signals can be heard mixed with each other.
On the other hand, the sound-with-sound editing method involves recording a sound signal on a first track of a magnetic tape and reproducing the sound signal by a first recording/reproducing head. A new sound signal is supplied with overlapping of a bias to a second recording/reproducing head provided for a second track of the same tape in line with said first recording/reproducing head, while the sound reproduced from the first track is heard. Thus the new sound signal is recorded on the second track separate from, but in synchronism with the sound signal previously recorded in the first track. When reproduced by simultaneously operating the first and second heads, the two sound signals from the first and second tracks can be heard mixed with each other. However, the "sound-on-sound" and "sound-with-sound" methods require at least two tracks on a common magnetic tape so that the tape recorder adapted to operate with only one track cannot perform such editing.
Therefore, the aforementioned magnetic recording type photographic film for recording picture with sound accompaniment is, because of the narrow width of said main stripe, impossible to use for the "sound-on-sound" and "sound-with-sound" methods. For this reason, the conventional sound motion projector is constructed with an erasing head and a recording/reproducing head arranged in the order in which the film is fed film is transported, so that when "double record" is performed, the erasing head is inoperative, and the recording/reproducing head is supplied with sound signal information overlapped on a bias. When "entire erase-record" is performed, both of the erasing and recording/reproducing heads are operative. In the latter connection, it should be explained that the film passes first over the erasing head to erase the, original sound signal recorded in the main stripe and then over the recording/reproducing head to record a new sound signal in the main stripe.
A conventional sound motion projector capable of "double record" and "entire erase-record" is however characterized by a lack of means by which the operator may listen to the sound reproduced from the original sound information when recording the new sound information. Accordingly, the position of that portion of the magnetic recording track which is subject to the double recording or the entire erase-recording operation has to be determined by the use of the operator's head or "sixth sense", while viewing the projected picture. If the operator is wrong, the necessary sound information may be erased by mistake when using the erase-record method and conversely unnecessary sound is left unerased through oversight. When double record is performed, the two sound signals tend to be undesirably displaced from one an other. Thus, with sound motion picture projector, it is very difficult to do sound editing and it can not be effected as accurately as desired.
One means to overcome the above mentioned drawbacks of the conventional sound motion projector, is proposed in connection with the sound editing for the conventional sound motion projector which uses a magnetic recording medium with only one track on a single main stripe such as sound film. According to this proposal, for erase-record the operator makes use of a means by which a reproducing head are arranged, erasing head and recording head in this order in the direction in which the film is fed. When the "entire erase-record" is performed, the original sound signal is first reproduced by the reproducing head. Then that sound signal is erased by the erasing head positioned behind the reproducing head, and the reproduced signal is heard. At the same time a new signal is fed together with a bias to the recording head positioned to the rear of the erasing head, so that the reproduced signal and the new signal are recorded in unison on the film. When double record is performed, the erasing head is operative, and the prerecorded signal is reproduced by the reproducing head. While listening to the reproduced sound, the operator controls supply of a new signal together with a bias to the recording head so that the reproduced signal and the new signal are recorded in unison on the film. However, this type projector is associated with an drawback; as the reproducing and recording heads are separated along the length of the film by an appreciably large distance, the sound-on-sound editing operation results in a displacement of the later recorded signal from the corresponding picture.
The presently available sound motion picture system is designed so that sound editing is performed mainly in the projector. Accordingly, almost no attempts have been made to eliminate the afore mentioned drawbacks by taking into account otherwise effective improvements of the sound motion picture camera.